383
FXUS63 KIND 011012
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
612 AM EDT Mon Sep 1 2025

.KEY MESSAGES...

- Quiet and dry weather through Monday Night.

- Near to below average temperatures to continue for much of this
week

- Next chance for rain arrives Wednesday and continues into early
Thursday followed by another round of cooler/drier air late week

&&

.SHORT TERM (Today and tonight)...
Issued at 256 AM EDT Mon Sep 1 2025

Surface analysis early this morning shows strong high pressure in
place across the eastern Great Lakes. This was resulting a cool and
dry easterly surface flow that we have seen the past few days.
Aloft, strong ridging was in place from the upper midwest to eastern
Quebec, providing subsidence over our area. A broad but weak upper
low was found over the middle Atlantic States. Dew points across
Central Indiana were mainly in the lower 50s. GOES16 showed clear
skies across the state, with clouds found over the plains where the
ridging and surface high had less influence.

Today and Tonight...

We will experience more changes to the overall weather pattern
today, but the impacts will result in little change in the overall
weather.

Our strong ridging in place to the north along with its associated
surface high pressure will continue to drift east as its exits the
eastward. Still, as this occurs through the course of the day and
tonight subsidence will remain in place. The departing high and
ridge will continue to become more elongated and remain across the
Great Lakes and keep a dry easterly flow across our area. This will
continue to result in a mostly sunny day and mostly clear night
tonight. Forecast soundings today and tonight remain dry across the
area showing unreachable convective temperatures. Thus very little
cloud cover is in store. With little overall change in the overall
airmass, highs today will again be in the upper 70s to near 80 with
lows tonight in the lower to middle 50s.

The upper pattern late tonight and into Tuesday is expected to show
strong ridging developing over the western CONUS, resulting in a new
source of subsidence. The northwest, lee side flow aloft of this
developing ridge will create a new area of high pressure over the
upper midwest and continue to influence our weather late tonight and
into Tuesday. A small caveat, a weak, cusp-like surface boundary is
set to develop late tonight and Tuesday near the Ohio River. This
may result in more cloud cover along with rain chances for Tuesday
mainly near the Ohio river.

&&

.LONG TERM (Tuesday through Sunday)...
Issued at 256 AM EDT Mon Sep 1 2025

Upper-level analysis shows large-scale troughing over the Midwest
and northeastern US. Ensemble guidance is in good agreement showing
this pattern holding steady through much of the forecast period. As
such, below-average temperatures are expected to continue through
the majority of the coming week.

The next decent chance of rain looks to be in the Tuesday/Wednesday
timeframe. Guidance is showing low pressure strengthening and
occluding to our north, with a cold front passing through the area
as well. Some surface moisture could creep north in response to the
deepening system. Rainfall amounts are still uncertain, and will
depend on the position and strength of the system along with how
quickly the cold front passes through. Amounts look light, though
guidance has been trending a bit wetter in recent runs. Thunderstorm
potential may lead to pockets of heavier rainfall as well.

Regardless of rainfall, an unseasonably cool air mass looks to drop
southward behind the front. ECMWF/GFS deterministic guidance shows
850mb temps between 3-6 degrees C, which could allow for low
temperatures potentially into the upper 30s assuming ideal
radiational cooling (clear skies and light winds). Blended guidance
has low to mid 40s, which seems reasonable for now given the
uncertainty in strength/position/timing of the occluding low. The
blend, however, shows highs in the mid to upper 60s Thursday and
Friday. This may be a bit pessimistic, since the sun angle is still
quite high and we have recently been running warmer than guidance
under optimal boundary layer mixing conditions.

Uncertainty in the larger-scale pattern returns this weekend, as
the ECMWF and GFS diverge regarding the longevity of deep troughing.
Both models do show the trough breaking down this weekend or shortly
after, with potentially warmer temperatures returning next week.
Rain chances look minimal this weekend into next week as the jet
stream shifts northward.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 612 AM EDT Mon Sep 1 2025

Impacts:

- None

Discussion:

No significant changes to the ongoing TAFs. GOES16 shows clear skies
across Indiana.

VFR Conditions are expected through the TAF period. Strong High
pressure over the eastern Great Lakes will continue to provide a
cool and dry lower level easterly flow. Forecast soundings appear
too dry through the period for CU development. A few passing hi CI
will be possible today.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...Puma
LONG TERM...Eckhoff
AVIATION...Puma